Vessel with retractable motor/generator assembly

ABSTRACT

Vessel comprising a motor/generator assembly ( 10 ), the motor/generator assembly ( 10 ) comprising a drive unit ( 11 ) and a propeller ( 12 ) attached to the drive unit ( 11 ) for providing propulsion to the vessel ( 1 ) or for generating electric power. The assembly ( 10 ) further comprises an attachment arm ( 13 ), the drive unit ( 11 ) and propeller ( 12 ) being attached to one end of the attachment arm ( 13 ), and an other end of the attachment arm ( 13 ) being attached to the vessel ( 1 ) by means of an actuator ( 15 ). The actuator ( 15 ) is arranged to extend the drive unit ( 11 ) and propeller ( 12 ) into the water and to retract the drive unit ( 11 ) and propeller ( 12 ) from the water.

FIELD OF THE INVENTION

The present invention relates to a vessel, e.g. a sailing vessel,comprising a motor/generator assembly, the motor/generator assemblycomprising a drive unit and a propeller attached to the drive unit forproviding propulsion to the vessel or for generating electric power.

PRIOR ART

Dutch patent NL1020217 describes an electric propulsion and generatorunit for sailing ships. A lifting arrangement is disclosed, which ispositioned in a steering column of the ship. The arrangement disclosedis complex, and takes up additional space inside the vessel: theelectric motor is positioned inside the vessel in both extended mode andretracted mode, and drive a propeller via a transmission and rotatingshafts.

American patent U.S. Pat. No. 6,802,749 discloses a trolling and batterycharging system for a vessel. The system has a fixed construction andcan only be positioned on an outer perimeter of the vessel. The systemis not retractable, but can only be removed in its entirety. This makesa stowing space on board of the vessel a necessity.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved motor/generatorassembly, which allows to provide a very energy efficient vessel.

According to the present invention, a vessel according to the preambledefined above is provided, in which the assembly further comprises anattachment arm, the drive unit and propeller being attached to one endof the attachment arm, and an other end of the attachment arm beingattached to the vessel by means of an actuator, the actuator beingarranged to extend the drive unit and propeller into the water and toretract the drive unit and propeller from the water. When using anattachment arm, it is possible to retract and extend the assembly veryefficiently, and also to obtain an efficient position of the drive unitand propeller away from the vessel itself (in a free water flow). In oneembodiment, the actuator comprises a swiveling actuator mounted above awater level of the vessel. Swiveling or rotation of the actuator can beimplemented very efficiently when space is available above the waterline of a vessel, e.g. as is the case with catamarans. Swiveling may beimplemented in a sideways direction, but in some circumstances,swiveling to the front or aft of the vessel is also a good possibility.In a further embodiment, the actuator comprises a linear actuatormounted in a hull of the vessel. The linear retraction and extension ofthe assembly is also very efficient, especially in the case of singlehull vessels. By proper positioning of the actuator, further advantagesmay be obtained, as improved center of gravity, control, etc.

The attachment arm has a streamlined shape in a further embodiment, e.g.in the form of an aerofoil shape. This allows to minimize the dragcreated by the part of the attachment arm extending in the water (and toa lesser extend also the drag created in air). In an even furtherembodiment, also the drive unit has a streamlined profile, e.g. the formof the front of a torpedo.

In a specific embodiment, the vessel comprises two hulls, both providedwith a motor/generator assembly. Having two assemblies allows a greateroperating range (having one or both assemblies working as motor orgenerator), and also allows to use the drive capability of bothassemblies for differential steering purposes. In a further embodiment,the propellers of the two motor/generator assemblies are counterrotating. This minimizes or even eliminates a wheel effect, allowing therudders to be used to full efficiency (no counter steering is necessaryto counteract the wheel effect).

In an even further embodiment of the present invention, the vesselfurther comprises a motor/generator electronics unit for controllingoperation of the drive unit and for converting electric energy, in whichthe motor/generator electronics unit further comprises a heat exchangerfor transporting heat energy from the motor/generator electronics unitto further onboard systems (such as warm water supply). This furtherenhances the efficiency on board of the vessel, as the heat generated inthe electronics unit is used to save energy in other onboard systems.

The motor/generator electronic unit is in an embodiment further arrangedto switch to a power generating mode when the electric motor exceeds apreset rotation speed. The preset rotation speed (rpm) may be a minimumrotation speed, below which no electric power can be generated by thedrive unit (e.g. 150 rpm). The preset rotation speed may also be higher,e.g. to allow to use the drive unit to propel the vessel, while changingto a power generating mode above a threshold rotation speed, e.g. tomake use of wind or water flow which propels the vessel to a higherspeed. The motor/generator electronics unit is in an even furtherembodiment also arranged to be in a propelling mode up to a maximumspeed of the electric motor. This allows to use the motor/generatorassembly most efficiently, as beyond a certain rpm, additional powerinput to obtain a higher speed is not efficient (e.g. when needing 30%more electrical power to obtain a speed increase of only 0.2 or 0.5knots). Usually the maximum rpm setting is related to the maximum hullspeed.

SHORT DESCRIPTION OF DRAWINGS

The present invention will be discussed in more detail below, using anumber of exemplary embodiments, with reference to the attacheddrawings, in which

FIG. 1 shows a cross sectional view of a part of a vessel according toan embodiment of the present invention;

FIG. 2 shows a cross sectional view in sailing direction of the vesselof FIG. 1;

FIG. 3 shows a detailed side view of a motor/generator assembly as usedin the vessel of FIG. 1;

FIG. 4 shows a partial detail view of the attachment of themotor/generator assembly of FIG. 3 to the vessel; and

FIG. 5 shows a simplified diagrammatic view of the elements of a vesselin which the present invention is embodied.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention may be advantageously applied in all sorts ofsailing vessels, such as catamarans. In FIG. 1, a cross sectional viewis shown of an exemplary implementation in a catamaran 1. Amotor/generator assembly 10 is fitted in the rear part of catamaran 1,but in front of the rudder 2. As visible in this view, themotor/generator assembly 10 comprises a drive unit 11, a propeller 12connected to the drive unit 11, and an attachment arm 13 for extendingthe drive unit 11 and propeller 12 into the water. This position of themotor/generator assembly 10 ensures that the rudders 2 stay effective,with minimum influence of the water flow which is disturbed by thepropeller 12 of the motor/generator unit 10 (no vibrations).

In FIG. 2, a cross sectional view of the catamaran 1 of FIG. 1 is shownin sailing direction, at the position of the attachment of themotor/generator unit 10 to a hull 3, 4 of the catamaran 1. This viewclearly shows the two-hull concept of the catamaran 1, having astarboard hull 3 and a port hull 4, connected to each other. Whensailing the water line 5 is low at each of the hulls 3, 4, as indicatedin FIG. 2. The attachment arm 13 is long enough to allow the drive unit11 and propeller 12 to be well below the waterline 5, in the extendedposition as shown with letter A. In the embodiment shown, the propeller12 is not close to the hull 3, 4, but at a distance of about one meter,allowing the propeller 12 to operate in a virtually undisturbed waterflow. The assembly 10 may be rotated out of the water into a retractedposition as shown with letter B. In the extended position A, each of themotor/generator assemblies 10 can act either as a propulsion motor (e.g.for entering a harbor), or as electricity generator. The attachment ofthe motor/generator assembly 10 to one of the hulls 3, 4 will beexplained below with reference to the FIGS. 3 and 4. By having the twopropellers 12 at port and starboard side to counter-rotate, wheel effectis avoided and efficiency is improved as the rudders 2 can then be keptin line instead of counter steering the wheel effect. Furthermore,having two motor/generator assemblies 10 in a single vessel 1 alsoallows to use differential steering, eliminating the need to make theassemblies 10 steerable. Differential steering is also more effectivethan using the rudders 2 only.

The retracted position B of a motor/generator assembly 10 may also beobtained by swinging the assembly to the front or aft of a vessel. Insome vessels 1 (e.g. narrower catamarans 1, or trimarans) this is easierto implement then sideways retraction. In an even further embodiment(e.g. in the case of single hull vessels 1), the motor/generatorassembly 10 may be retracted and extended in a vertical direction, e.g.using a linear actuator 15 or a lifting cylinder. In that case, aclosing lid may be provided to close off the hull when the assembly isin retracted position.

As the motor/generator assemblies 10 may be retracted from the waterwhen not in use, numerous advantages are created. The resistance whilesailing is lowered, and actual sailing speed may increase as noconventional sail drives (usually diesel engine driven), propellers,propeller shafts, shaft supports are in the flow of the water. As aresult of the mounting position of the motor/generator assemblies 10,the heavy parts are located close to the centre of gravity of thecatamaran 1, which makes the catamaran 1 safer and more comfortable.Furthermore, when the catamaran 1 picks up too much speed (for comfortor safety), the motor/generator assemblies 10 may be lowered in theextended position A to increase resistance (lowering the speed) while atthe same time generating electrical power. The retractable nature of theassemblies 10 also allow beaching of the vessel 1 without causing anydamage to the drive unit 11 or propellers 12.

A further advantage of the present implementation in which thepropellers 12 are lifted from the water, is that no folding orfeathering propellers are needed, which are expensive and need regularmaintenance. Grounding of the entire catamaran 1 with the presentmotor/generator assembly 10 is very limited, which will cause propelleranodes (if present) to wear very slowly, if at all. The propellers 12are of a material which lessens or eliminates corroding of the propeller12 and repels growth thereon, which allows the propeller 12 to retainits original efficiency without degradation over time. Because of thelimited grounding, the chance of lightning strike on the catamaran 1 isless. A further advantage of the present construction of the catamaran 1with motor/generator assembly 10 is that the drive unit 11 and thepropeller 12 are located under the bridge deck between the hulls 3, 4,and therefore noise in the rooms or quarters in the catamaran 1 can beminimal.

In the deck connecting the hulls 3, 4, a hatch 6 (or two hatches) may beprovided which allow inspection of the drive unit 11 and propeller 12when in the retracted position B. The hatch 6 also allows quick and easycleaning of the propeller 12 or drive unit 11, e.g. when fouled withkelp, ropes or fishing nets.

The use of two motor/generator assemblies 10 in a catamaran 1 allowsusing one or both assemblies 10 either for propulsion or for generatingelectricity. Also, it is possible to use one of the assemblies 10 asmotor or generator, and lift the other assembly 10 from the water,thereby decreasing resistance.

The motor/generator assemblies 10 may be attached to the respective hull3, 4 above the waterline 5, which prevents any possible locations forleakage of the hull 3, 4. In FIG. 3 a more detailed side view is shownof the motor/generator assembly 10, including the attachment elementsfor mounting the assembly 10 to the hull 3, 4. Also, this particularview shows more in detail that the drive unit 11 is streamlined (e.g.the combination of drive unit 11 and propeller 12 have a torpedo likeshape) which allows to keep the resistance of the assembly 10 in thewater as low as possible. The electric motor/generator 27 (see FIG. 5)in the drive unit 11 is in an embodiment of a brushless type(maintenance free). Various power ratings may be provided by the motor27, depending on the specific type of vessel, and may range from 3 up to50 kW. The drive unit 11 is built to IP68 standard, so it is possible touse them in the water without further measures. Furthermore, theelectric motor/generator 27 in the drive unit 11 may be preheated beforeoperation, to prevent any possible condensation inside the drive unit11. The outside of the drive unit 11 may be made from (polished)aluminium, greatly improving the corrosion resistance, and hence theflow resistance.

In FIG. 4 a partial detail view is shown of the attachment of themotor/generator assembly 10 to the hull 3, 4 of a catamaran. A hullplate 18 has generally a rounded shape, and an inner support 19 isprovided on the inside of the hull 3, 4. On the outside of the hullplate 18, a swing support 17 is provided, which can be mounted to theinner support 19 using e.g. bolts. Also, the mounting element 16 arevisible, which mount the attachment arm 13 to a rotary actuator 15, andallows a rotary movement of the motor/generator assembly 10 of more than90°, e.g. over 110°.

Using the present embodiment of the motor/generator assembly 10 and theattachment structure as shown in FIGS. 3 and 4, there is no need for ashaft penetrating the hull 3, 4 of the catamaran 1, or other complex andresistance causing attachment structures. This further enhances the lowresistance and efficiency of the entire vessel 1.

The efficiency of the motor/generator assembly 10 is furthermoreimproved by using a streamlined type of attachment arm 13, e.g. using anaerofoil profile to minimize flow resistance in the extended position A.In this embodiment, a large three-bladed propeller 12 is used, which isof a slow rotating type and light weight, which further increases theefficiency of the motor/generator assembly 10. To further increase theefficiency of the propeller 12, a ring may be provided at thecircumference of the propeller 12, which then acts as a jet fan.

The drive unit 11 (with attached propeller 12) is attached to one sideof the attachment arm 13 using mounting elements 31, e.g. using astraight plate attached to the drive unit 11, which is bolted in placein the attachment arm 13 as shown. At the opposite side of theattachment arm 13, further mounting elements 16 are provided allowingmounting the motor/generator assembly 10 to the hull plate 18, e.g.using the swing support 17 and an actuator 15. The rotary actuator 15 isprovided in the swing support 17, which allows moving the entiremotor/generator assembly 10 between the extended position A andretracted position B. The rotary actuator 15 may be of a hydraulic type,or of an electrical type and in case of emergence can also be liftedmanually with a hand pump.

In FIG. 5, a simplified diagrammatic view is shown of elements of thepresent invention playing a role in improving the energy efficiency of amodern sailing vessel 1. The drive unit 11 is connected to amotor/generator electronics unit 20 (e.g. using a cable 14 (see FIG. 3)running through the attachment arm 13). This unit 20 is coupled to abattery 26 (or other storage for electrical power, such as accumulatorsor storage capacitors), and controls the flow of electrical energy fromor to an electric motor 27 in the drive unit 11 (either charging thebattery 26, or depleting the battery 26). This allows using themotor/generator assembly 10 to provide thrust in one instance, and toprovide electrical energy in another instance (e.g. when sailing, i.e. apart of the wind energy from the sails will be transferred to charge thebattery 26).

The motor/generator electronics unit 20 comprises electrical circuitsfor controlling and converting energy, i.e. using high powersemiconductor elements. In the process of control and conversion, heatis generated in the electronics unit 20, which in conventionalcircumstances is passed to the environment, e.g. using cooling ribs andcirculating air. However, in the present invention embodiments, the heatgenerated by the electronics unit 20 is saved, using heat exchangers 21,22 and associated fluid channels 23, 24 (e.g. water in pipes or tubing).This allows to transfer energy (heat) from the electronics unit 20 toother onboard systems in the sailing vessel 1, e.g. a warm water supply25. The warm water supply 25 may e.g. use a boiler to store the heatedwater. As the heat is transferred to the warm water supply 25, thereturn channel 24 transports cooled water (or another suitable fluid)which allows cooling of the electronics unit 20. In turn, this increasesthe efficiency and life time of the electronics unit 20.

In a further embodiment, the motor/generator electronics unit 20 is alsoused to supply power to an onboard electrical heating system (for spaceheating or water heating). The heating system may then be adapted tooperate on e.g. a 120 VDC power supply incorporated in the electronicsunit 20, which is easier and more efficiently than running the heatingsystem on 110 or 220 VAC (which requires first a conversion to 12 VDCand then to 110 or 220 VAC using an inverter).

The motor/generator electronic unit 20 is furthermore arranged tocontrol the operation of the electric motor 27 of the drive unit 11.Several modes of operation are possible:

-   -   The drive unit 11 may be preset at an rpm setting, either using        the drive unit 11 or the sails to thrust the vessel 1. When the        speed of the vessel 1 picks up (because of waves, increased wind        force, etc.), and consequently the electric motor 27 exceeds a        preset rotational speed, the operation of the drive unit 11 is        automatically changed to a power generating mode to charge the        battery 26.    -   Maximum and minimum rpm settings can be preset, e.g. to use the        least possible amount of energy or to charge the battery 26 most        efficiently. When charging normally starts at 120 rpm of the        electric motor 27 of the drive unit 11, and below that setting,        no efficient generation of electrical power is possible. The        maximum rpm setting may be related to the maximum hull speed.        E.g., when the hull speed is nine knots, and the associated        drive unit 11 must be run at 900 rpm to reach that speed, the        maximum rpm setting may be set at 950 rpm. Driving the        electrical motor 27 of the drive unit 11 beyond 950 rpm is not        efficient, as the additional consumption of electrical energy is        not transferred in an equal increase in speed (e.g. at 1100 rpm,        only 0.2 knots additional speed is obtained, but at 30% higher        power consumption).    -   Safety modes may be included for the case of a stuck propeller        12, overheating of the electric motor 27 of the drive unit 11,        etc. When overheating occurs, the electronics unit 20 lowers the        drive rpm, and eventually stops the electric motor 27 of the        drive unit 11.

The electronics unit 20 is connected to other onboard systems 28 in afurther embodiment, e.g. using RS232 or USB connections. Other onboardsystems 28 include, but are not limited to, radar system, (GPS)navigation system, etc. Also monitoring equipment may be interfaced withthe electronics unit 20, e.g. for monitoring temperature of the driveunit 11, temperature associated electronics, motor rpm, torque,electrical consumption, etc. When e.g. overheating occurs, appropriatemeasures can be taken (e.g. shutting down or transition to lower loadoperation). When desired, an optional generator 7 (see FIG. 1) may beinstalled in the vessel 1, to provide additional electric capacity foronboard systems, or for back-up purposes. The optional generator 7 ismounted sound proof, to avoid sound or vibration nuisance to the peopleon board.

Using the motor/generator assembly 10 in the embodiments of the presentinvention allows operating a sail vessel 1 in a very efficient andenvironmentally friendly manner. When using the assembly 10 forpropelling the vessel 1, the fuel consumption is much less than withconventional diesel or diesel-electric propulsion. The weight of theassemblies 10 is also lower than comparable conventional propulsionsystems. When using the assembly 10 for electric propulsion of thevessel 1, there is no exhaust smell, smoke, noise, vibration, as inconventional systems, and it is also not necessary to fill diesel orpetrol tanks in each port. Furthermore, the cost of maintenance, fuel,and downtime are considerable less compared with conventional propulsionsystems. Space normally occupied on a vessel 1 for the conventionalpropulsion system, may now be used for other purposes (storage space,additional buoyancy, etc.).

1-9. (canceled)
 10. A vessel comprising a motor/generator assembly (10),the motor/generator assembly (10) comprising a drive unit (11) and apropeller (12) attached to the drive unit (11) for providing propulsionto the vessel (1) or for generating electric power, in which theassembly (10) further comprises an attachment arm (13), the drive unit(11) and propeller (12) being attached to one end of the attachment arm(13), and an other end of the attachment arm (13) being attached to thevessel (1) by means of an actuator (15), the actuator (15) beingarranged to extend the drive unit (11) and propeller (12) into the waterand to retract the drive unit (11) and propeller (12) from the water.11. The vessel of claim 10, in which the actuator (15) comprises aswiveling actuator (15) mounted above a water level of the vessel (1).12. The vessel of claim 10, in which the actuator (15) comprises alinear actuator mounted in a hull of the vessel (1).
 13. The vessel ofclaim 10, in which the attachment arm (13) has a streamlined shape. 14.The vessel of claim 10, in which the drive unit (11) has a streamlinedprofile.
 15. The vessel of claim 10, in which the vessel (1) comprisestwo hulls (3, 4), both provided with a motor/generator assembly (10).16. The vessel of claim 15, in which the propellers (12) of the twomotor/generator assemblies (10) are counter rotating.
 17. The vessel ofclaim 10, further comprising a motor/generator electronics unit (20) forcontrolling operation of the drive unit (11) and for converting electricenergy, in which the motor/generator electronics unit (20) furthercomprises a heat exchanger (21, 22) for transporting heat energy fromthe motor/generator electronics unit (20) to further onboard systems(25).
 18. The vessel of claim 17, in which the motor/generatorelectronic unit (20) is further arranged to switch to a power generatingmode when the electric motor (27) exceeds a preset rotation speed. 19.The vessel of claim 18, in which the motor/generator electronics unit(20) is further arranged to be in a propelling mode up to a maximumspeed of the electric motor (27).